In material handling systems in which a stream of discrete articles are transported from one location to another through a number of stations where particular operations are performed upon them, it is often necessary to elevate or lower the articles to reach a desired destination. Ramps composed of moving belts or rollers may be effective in lowering a stream of conveyed articles, but because of the shallow incline required for effective upward conveyance, usually require excessive length when space is at a premium.
Vertical lift devices employing a series of carriages connected to one or more sprocket-driven chains are well known. One type employs a single sprocket-driven chain with evenly spaced carriages rotatably connected to the chain. The carriages have spaced tines which extend outwardly from the chain and which pass through alternately spaced tines placed in the path of the carriage at infeed and outfeed stations. An article is lifted from the infeed station along the upward flight of the carriage and is deposited at an outfeed station at a higher elevation on the downward flight of the carriage. In order to stabilize the carriages it is known to provide rollers which engage in fixed tracks.
In order to avoid excessive loads on the drive chain, vertical lifts have been developed which employ a pair of sprocket driven chains spaced on either side of the carriage with the carriage connected therebetween. In conveyors of this type, however, the carriage tines commonly extend outwardly from the two chains and are limited to restricted infeed and outfeed positions.
Conventional lift apparatus are often extremely noisy and must be carefully supervised because of the tendency of articles to become dislodged from the desired lifting path due to carriage instability. These characteristics are exagerated at higher speeds of lift operation.
In certain installations it is necessary to feed articles in to the front of the lift and feed them out at the side. In other installations it is necessary to feed articles both in and out from the front or both in and out from the sides. Conventional vertical lifts require widely different lift apparatus to fulfill the requirements of these varying directional changes.
What is needed is a vertical lift which will accept articles from either the front or the side and may feed articles out from either the front or the side, which reliably and steadily conveys articles at a desired pace, and which is economical to manufacture and maintain under a variety of conditions.